In Conversation: Andrea Secco on Dissolved Gas Analysis in Water

At its core, it’s about measuring gases that are dissolved in a liquid matrix, typically water, so you can interpret physical processes (like recharge and mixing), chemical processes (like oxidation and disinfection by-products), or biological processes (like respiration, methanogenesis, and denitrification).

The key is that dissolved gases are often time-sensitive. Concentrations can change during sampling, transport, or storage. That’s why membrane inlet mass spectrometry is so useful: it provides real-time insights that traditional methods can’t match, enabling precise monitoring at trace levels rather than waiting on slow lab workflows.

MIMS uses a semi-permeable membrane as an interface between the liquid sample and the mass spectrometer: dissolved gases diffuse through the membrane and enter the analyser, enabling rapid, sensitive measurement of multiple species.

The practical advantage is speed + sensitivity. You can monitor changes in dissolved gas composition in real-time, and that’s incredibly useful when your signal is small or transient.

A few recurring themes come up across groundwater, surface water, estuary, and wastewater work:

• N2, O2, Ar for gas balance, biological activity, and process interpretation (especially for denitrification studies).
• CO2 for respiration rate and carbonate system dynamics, which influence pH and ecosystem health.
• CH4 for methane generation and control (environmental monitoring and process studies).
• Isotopes like Deuterium or Oxygen-18 to identify water sources and map water movement.
• Trace-level contaminants and volatile species where low-level monitoring really matters.

And then you have specialised cases like noble gases (e.g., helium, krypton, xenon) when teams are doing groundwater dating or tracing recharge histories.

The HPR-40 MIMS is a strong fit when you want bench-top stability and ultra-sensitive dissolved species analysis in a controlled lab environment, with the flexibility to address different sample types.

It’s designed for gas monitoring in liquids at sub-ppb levels, with a standard mass range of 200 amu, and it’s available with a broad range of sampling inlets, including options that help with small volume samples and specialist studies.

From a workflow perspective, it’s ideal when you need repeatable, high-confidence data for reporting, method development, or longer monitoring runs.

The pQA is the solution for field-based dissolved gas measurements—at the riverbank, on boats, or in mobile labs—where you want real-time analysis without relying on sample preservation and transport.

It features sub-ppb detection, 200 amu mass range (with 300 amu option), and it’s supplied in a Pelican® case with flexible powering: 12 V for field use (battery/solar) or 220 V for lab operation.

So, if your project depends on analysing the sample directly at the source, the pQA changes what’s feasible and removes the risks of sample collection and transport like:

• Degassing during collection and transfer (you lose the species you are interested in).
• Temperature effects changing solubility and biasing concentrations.
• Headspace formation in containers.
• Time delays allowing biological or chemical processes to continue “in the bottle.”

In denitrification research, the goal is often to distinguish background signals from those generated by biological processes. This makes stable ratio measurements and high precision essential, as findings usually depend on subtle differences.

This is especially critical in areas like marine denitrification studies, where MIMS effectively meets scientists’ needs for accurate and reliable quantitative data.

Groundwater geochronology often benefits from high noble gas sensitivity, because the concentrations can be extremely low and the interpretation depends on accurately resolving those species.

Hiden offers a specialist X44 polymer membrane in a large circular cell configuration aimed at high sensitivity for noble gases such as helium, krypton, and xenon. That kind of targeted membrane/inlet optimisation is important in real-world geochronology workflows.

It’s a good example of how dissolved species analysis isn’t only for academic environmental science. In pools or recreational water, teams can be concerned about harmful disinfection by-products (DBPs), and the measurement challenge is often low concentration monitoring and ensuring you can see changes quickly.

Hiden explicitly references this type of application in the HPR-40 MIMS overview, which reflects the broader point that dissolved gas/vapour monitoring has practical health and compliance drivers, not just research drivers.

I usually frame it as: 

• HPR-40 MIMS if your priority is bench-top performance, controlled conditions, and long-term stability for dedicated laboratory workflows.
• pQA if your priority is field deployment and immediacy, measuring at the point of sampling, with portable power options and a rugged transport case.

It’s worth noting that the HPR-40 MIMS is built on a modular platform: if your research focus shifts, you can easily swap the membrane inlet for any of our other sampling options.

Additionally, the pQA can be removed from its Pelican® case for standalone use on a lab bench.

The direction is toward:

• High-frequency, in-situ monitoring (how concentrations change over time in response to natural events).
• Higher confidence in low-level signals (trace contaminants, noble gases).
• Simultaneous detection of multiple species (particularly important in denitrification studies).

Ultimately, these trends point toward a need for greater analytical agility. Whether it’s the push for sub-ppb detection of noble gases or the requirement for real-time data in remote locations, the future of dissolved gas analysis belongs to systems that can bridge the gap between the field and the lab.

By prioritizing modularity and high-speed multi-species detection, we ensure that, as the questions in environmental science evolve, your instrumentation is already equipped to provide the answers.

Learn more about the HPR-40 MIMS and the pQA.

For further details, technical support, or to discuss your application with Andrea Secco, please contact us.